Can you see those ponds from the road? If so, did they stay mostly full during the drought? Those would be good signs (though not proof) that you have decent soils to make a pond and enough rain to keep it mostly full.
Also, your land is steeper. A steeper slope causes MORE surface water run off (if all other factors are equal).
You do not HAVE to clear the trees in your watershed, but woods generally have a little less surface run off than grasslands. If you do clear some of the trees in the watershed, that might be part of your first priorities. On steep land, you want to have grass established before the rains fill your pond or the silt will steal some of your depth.
It is difficult to build the perfect sized pond due to all of the complex variables. However, if your pond is initially too large for the supporting watershed, then pushing up some swales to direct more water to the pond can be done after a few years of observing your conditions.
Another option would be to build a little forage/grow out pond upslope in the same gully as your main pond. If you do get a damaging drought, you can seine that pond and drain the remaining water to supplement your main pond.
Just throwing out more ideas while you are still in the planning stages.
